(±)-3-[3-[(1RS,2RS,4SR)-bicyclo[2.2.1]hept-2-yloxy]-4-methoxyanilino]-2-methyl-2-cyclopenten-1-one is known to have a strong PDE IV inhibitory activity and to exhibit a bronchodilating and anti-inflammatory activity (see, for example, Japanese Unexamined Patent Publication (Kokai) No. 11-189577) and is considered effective for inflammatory diseases such as asthma, dermatitis, autoimmune diseases such as rheumatism, multiple sclerosis, etc.